2-D Material Source-Drain Contacts for Low-Resistance Semiconductor Channels
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Solution Overview
Problem
The challenge in the semiconductor industry is to form reliable semiconductor devices at increasingly smaller sizes due to the complexity and difficulty of fabrication processes as feature sizes decrease, leading to issues with carrier transport and photocurrent efficiency in phototransistors.
Innovation Solution
The use of 2-D material layers such as graphene and transition metal dichalcogenides (TMDs) in semiconductor devices, where graphene serves as a channel layer and TMDs as a light absorption layer, with graphene electrodes positioned underneath the TMD channel layer to enhance carrier transport and photocurrent collection, and the incorporation of interlayer electrodes between adjacent 2-D material layers to improve drain current efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are decreased to increase functional density, then production efficiency is improved and costs are lowered, but fabrication process difficulty increases and reliability deteriorates
Solution Approach 1:
The patent changes the material parameter from conventional semiconductors to 2-D materials (graphene, TMDs), which fundamentally alters the electrical and optical properties. This material parameter change enables reliable device operation at smaller feature sizes by providing superior carrier mobility and photocurrent efficiency, thus resolving the reliability deterioration that occurs during scaling down.
Solution Approach 2:
The patent employs composite material structures combining different 2-D materials (graphene channel layer with TMD light absorption layer) to achieve both high carrier transport efficiency and effective light absorption. This composite approach maintains device reliability at small feature sizes by leveraging the complementary properties of each material layer.
2Ease of manufacture
If conventional materials are used in phototransistors, then fabrication is simpler, but carrier transport and photocurrent efficiency are insufficient
Solution Approach 1:
The patent changes the material parameters to 2-D materials with superior electrical and optical properties. Graphene provides exceptional carrier mobility while TMDs offer direct bandgap for efficient light absorption, fundamentally improving carrier transport and photocurrent efficiency compared to conventional materials.
Solution Approach 2:
The patent transitions from three-dimensional bulk materials to two-dimensional material layers, enabling precise control of material thickness and interface properties. This dimensional change allows for optimized carrier transport paths and enhanced light-matter interaction, significantly improving phototransistor performance.
3Reliability
If 2-D material layers are used to improve carrier transport, then photocurrent efficiency is enhanced, but contact resistance becomes a limiting factor
Solution Approach 1:
The patent introduces graphene as an intermediary material between the metal electrodes and the TMD channel layer. Graphene's superior electrical conductivity and atomically thin structure create low-resistance contact interfaces, mediating the connection between metal and semiconductor while minimizing contact resistance and maximizing photocurrent efficiency.
4Productivity
If feature sizes are reduced, then functional density increases, but growth and etching challenges increase
Solution Approach 1:
The patent segments the phototransistor structure into distinct 2-D material layers (graphene channel layer, TMD light absorption layer) that can be independently synthesized and characterized. This segmentation allows each layer to be optimized separately using appropriate growth techniques, simplifying the overall manufacturing process despite small feature sizes.
Solution Approach 2:
The transition to two-dimensional material layers provides precise control over thickness and lateral dimensions, enabling accurate feature size definition without relying on conventional lithographic limitations. This dimensional approach facilitates the formation of small features with well-defined boundaries, reducing etching challenges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in significant drain current enhancement and improved device performance by facilitating easier current flow through the MoS2/graphene interface with lower contact resistance, and allows each 2-D material layer to contribute to the drain current, overcoming growth and etching challenges associated with smaller feature sizes.
Implementation Method 1
graphene serves as a channel layer... with graphene electrodes positioned underneath the TMD channel layer to enhance carrier transport
Implementation Method 2
TMDs as a light absorption layer... improved device performance by facilitating easier current flow through the MoS2/graphene interface
Data Source
AI summary
A semiconductor device includes a 2-D material channel layer, a gate structure, and source/drain electrodes. The gate structure is over a channel region of the 2-D material channel layer. The source/drain electrodes are over source/drain regions of the 2-D material channel layer, respectively. Each of the source/drain electrodes includes a 2-D material electrode and a metal electrode. The 2-D material electrode is below a bottom surface of a corresponding one of the source/drain regions of the 2-D material channel layer. The metal electrode is over a top surface of the corresponding one of the source/drain regions of the 2-D material channel layer.